Multiple grinding wheel



Jan. 6, 1959 L. H. METZGER 2,867,063

MULTIPLE GRINDING WHEEL Filed Feb. 2a, 1956 2 Sheets-Sheet 1 United States Patent MULTIPLE GRINDING WHEEL Leopold H. Metzger, Glencoe, lll., assignor to Super-Cut, Inc., Chicago, Ill., a corporation of lillinois Appiication February 28, 1956, Serial No. 568,318 Claims. (Cl. 51209) The present invention relates generally to grinding wheels. More particularly the invention relates to that type of grinding wheel which is known in the art as a multiple grinding wheel, is adapted primarily for grinding glass and other material, comprises a rigid disc-like body having means for fixedly connecting its central portion to one end of a power driven shaft and embodying on its front or forward face a plurality of circular spaced apart concentrically arranged grinding annulae, has the grinding annulae arranged so that the forward abrading or grinding surfaces thereof are in such regular stepped or offset relation that the forward surface of the innermost or smallest grinding element is spaced forwardly from the forward face of the body a greater distance than the forward surface of the outermost or largest annulus, and is adapted to be used by first positioning the glass so that the surface thereof that is to be ground is adjacent to, and in parallel and offset relation with, the forward face of the body and then effecting relative movement of the glass and the wheel in a plane at right angles to the axis of the wheel to the end that in connection with drive of the wheel the foremost grinding annulus first grinds the adjacent surface of the glass to a certain depth and then the other annulae successively grind said adjacent surface of the glass to progressively greater depths.

One object of the invention is to provide a multiple grinding wheel which is an improvement upon, and has certain inherent advantages over, previously designed grinding wheels of the aforementioned type, and is characterized by extremely high efficiency and comparatively low cost of fabrication and operation.

Another object of the invention is to provide a multiple grinding wheel of the type under consideration and in which the forward regions of the outer and inner peripheral side portions of the circular grinding annulae are shaped or bevelled so that they are of progressively decreasing radial width in a forward direction in order that the wheel in connection with use thereof grinds at a rapid rate of speed and without likelihood of chipping or fracturing the glass or other material being ground.

Another object of the invention is to provide a multiple grinding wheel of the type and character under consideration and in which each of the circular grinding annulae is in the form of an annular series of substantially equidistantly spaced arcuate segments.

Another object of the invention is to provide a multiple grinding wheel of the last mentioned character and in which the arcuate segments that form or constitute the circular grinding annulae consist of rear body parts and in addition forward abrasive parts which are soldered or otherwise fixedly secured to the forward faces of the body parts and are in the form of diamond or other abrasive particles together with metallic matrices in which the particles are imbedded.

Another object of the invention is to provide a multiple grinding wheel of the type and character last mentioned and in which the end faces, as well as the inner and outer peripheral sides of the abrasive parts of the arcuate seg- "ice ments are shaped or bevelled so that they are of progressively decreasing width in a forward direction in order that the grinding efficiency of the abrasive parts of the segments is materially increased.

Another object of the invention is to provide a multiple grinding wheel of the aforementioned character and in which the front face of the disc-like body is provided with a plurality of circular radially spaced concentric grooves in which the arcuate grinding segments fit snugly in order that the segments are non-compliant and are positively locked against radial displacement with respect to the wheel body.

Another object of the invention is to provide a multiple grinding wheel of the type and character under consideration and in which the arcuate segments are provided'with simple and novel arrangements whereby in connection with wear or truing of their abrasive parts they may be adjusted forwardly away from the front face of the body to thedesired extent and then releasably locked inplace. f

A further object of the invention is to provide a multiple 4 grinding wheel of the aforementioned type and in which the disc-like body is provided .with a simple and novel in groove and duct arrangement for delivering a liquid coolant onto the abrasive parts of the arcuate segments.

A still further .object of the invention is to provide a multiple grinding wheel which is generally of new and improved construction, eifectively and efiiciently fulfills its intended purpose, and involves a simple and novel ar- Figure 1" is a front view showing a multiple grinding wheel embodying the invention and illustrating in detail the arrangement, design and manner of mounting of the arcuate segments that constitute or form the plurality of circular spaced apart concentrically arranged grinding annulae;

Figure 2 is a fragmentary rear view of the wheel;

Figure 3 is a section taken on the line 3-3 of Figure l and showing invdetail the groove and duct arrangement for delivering a liquid coolantonto the abrasive parts of the arcuate segments;

Figure 4 is an enlarged fragmentary section illustrating. the wheel in operative or grinding relation with a piece of' glass and showing in detail the manner in which the forwardly or largest grinding element first grinds the adjacent surface of the glass to a certain depth and then the other elements successively grind said adjacent surface of the piece of glass to progressively greater depths;

Figure 5 is an enlarged section taken on the line 5-5 of Figure 3 and illustrating in detail the construction or design of the arrangements or means whereby the segments in connection with wear may be adjusted forwardly away from the front face of the disc-like body to the desired extent and then releasably locked in place; and

Figure 6 is an enlarged section on the line 6-6 of Fig ure 3.

The multiple grinding wheel which is shown in the It is designed primarily for use in wheel is shown in operative or grinding relation with a fiat glass piece 7. The wheel is preferably located above the glass piece and the latter is mounted on a horizontally movable support (not shown) so that it may be moved or fed relatively to the wheel in a plane that is parallel to the-upper surface of the glass piece-to be ground. As its components or parts the grinding wheel comprises a disc-like body 8 and three circular spaced apart concentrically arranged grinding'annulae:9, 10 and'll on what may be considered the front face of the body 18.

Whereas the wheel has beenillustrated and described as having three grinding annulae, it is to be understood that the wheel may 'havetwo grinding annulae or more than three grinding annulae depending upon'the character of the glass-or other-material to be ground and the nature or type of grinding.

The disc-likebody-8 'is formed of any suitable metal such'for example as steel, bronze or brass and has in the central portion thereof a circular hole 12 in which said one end of the aforementioned power driven shaft fits. Any suitable means (not shown) may be employed in order to connect the body'fixedly to the shaft and so that it is truly at right angles to the shaft axis. The hole 12 is arranged so that the axis thereof is truly at right angles to the front and rear faces of the body. The

body is; provided on its front face with six integral outwardly-extending circular spaced apart concentrically arranged ribs 1-3, 14, 15, 16, 17 and 18. The ribs 13 and 14 constitute a coacting outer pair and form or define between 'theman annular groove 19 in which the circular grindingannulus 9 is -mounted. ,The ribs 15 and 16 are disposed an appreciable distance inwards of the rib 14. They constitute a coacting intermediate pair and form or define-between them an annular groove in which thecircularfgrinding annulus 10 is mounted. The ribs 17 and-18 are-disposed an appreciable distance inwards of the rib 16 and together constitute acoacting inner pair. They former define'between them-an annular groove 21 for mounting of the circular-grinding annulus 11.

The circular grinding annulus 9 is the largest of the three grinding annulae and is of composite character in that'it consists of an annular series of equidistantly spaced arcuate segments 22. The latter are. in the form of rear body parts 23 and forward abrasive parts 24. The body parts 23 of the arcuate segments'22 are formed of steel,-bronze ,-brass or any other suitable solid and rigid non-abrasive material. They are of appreciably greater thickness-than the-annular groove 19 is deep and have the inner and outer sides thereof shaped conformably to and fitting snugly within said groove 19 so that the arcuate segments 22 are positively locked or retained against'radial' displacement with respect to the disc-like body 8. The abrasive parts 24 of the segments 22 are soldered or otherwise'fixedly secured or bonded to the body parts 23 and consist of matrices and diamond or other abrasiveparticles. Thelatter are imbedded in the matrices and are preferably distributed substantially uniformly-throughout said matrices. It is contemplated that the circular grindingannulus 9 will effect rough grinding of the glass to be ground and hence the diamond or other abrasive particles that constitute a part of the abrasive parts 24 will be of coarse mesh, as for example, 100 to l' lO'mesh. The forward surfaces of the abrasive parts-24*are shown to be fiat although they may in some instances, ifdesired, be convex or rounded in a radial or transverse direction. If these surfacesare fiat as shown,-such surfaces are arranged. or positioned'so that they lie in an imaginary plane that is at true right angles to'the axis of the body 8. The outer and inner arcuate sides of the abrasive parts 24 are shaped or bevelled so that the segments are of progressively decreasing radial width ina forward direction in order that the circular grinding element 9 in connection with use of the wheel grinds at a rapid'rate of speed and without likelihood of chipping or fracturing of the glass beingground. If the outer periphery porthey present more abrasive particles for grinding purposes and thereby decrease the time of grinding and materially reduce unit pressure on the abrasive particles by distributing the pressure of grinding over a large number of abrasive particles instead of a small number of particles. By having the peripheral sides of the abrasive parts 24 bevelled as shown instead of bevelled reversely the glass or other piece being ground is urged or wedged downwards into firm contact with its support instead of upwards towards the wheel and away from its support. The ends of the-abrasive parts 24 are likewise shaped or bevelled so thatthey'are of progressively decreasing width in a forwarddirection in order that the grinding efficiency of said parts 24 is materially increased. If the end portions of the outer abrasive parts are straight bevelled as shown in the drawings instead of being round bevelled the :angleofbevel is preferably 45.

it is contemplated that the outer side surfaces of the abrasive parts 240:? the arcuate segments 23 will be positioned at a certain predetermined distance from the front face of the disc-like body 8. In order to compensate or adjust for wear and also to permit of accurate truing in connection with original assembly each arcuate segment 22 is provided with a screw arrangement Whfl3- by it may be adjusted forwardly away from the body front face and then releasably locked in place. Such screw arrangement for each of the arcuate segments 22 consists-of an outer pair of feed or adjusting screws 25 and an inner pair of locking screws 26. The feed screws 25 extend through screw threaded holes 27 in the outer portion of the disc-like body 8 and are so arranged or positioned that their outer ends abut against the end portions of the inner radial surfaces of the body parts 23 of the arcuate segments 22 as shown in Figure 5 of the drawings. The inner ends of the feed screws 27, i. e., the ends that are adjacent to the rear face of the wheel body are provided with kerfs 28 in order that the screws may be turned by. a screwdriver or other turning tool. When the feed screws ,25 are turned so as to feed forwardly in the direction of the front face of. the wheel body, they move the arcuate segments 22 away from the body of the wheel. It is contemplated that the segments will only be moved forwardly sufficiently to compensate for wear of the abrasive parts 24 or to effect the desired truing. The locking screws 26 are disposed inwards of the feed screws 25 and extend loosely through cylindrical holes 29in thewheel body 8. The outer ends of the locking screws 26 fit within screw threaded sockets 30 in the body parts 23 of the arcuate segments 22, and the inner ends of said locking screws embody enlarged heads 31 which fit within counterbores 32 at the inner ends of the holes 29 and normally abut against annular shoulders 33 at the inner ends of the counterbores. The enlarged heads 31 of the locking screws 26 are provided with kerfs 34 whereby the screws may be turned by a screwdriver or other suitable turningtool. When the locking screws are tightened, they serve to clamp the arcuate segments 22 against the outer ends of the feed screws 25. In connection with adjustment of the segments 22 for wear compensating or other purposes, it is contemplated that the locking screws 26 will first be loosened in order .to release the segments and then the feed screws 27 will be adjusted to the proper extent to cause the outer side surfaces of the abrasive parts 24 to be spaced the proper distance from the front face of the disc-like body 8. Thereafter the locking screws will be tightened in order releasably to lock the arcuate segments 22 in their adjusted position. Preferably -the arcuate segments 22 that constitute the outermost circular grinding element 9 are spaced apart a distance materially less than their length (see Figure 1).

The circular grinding annulus 10 is the second largest of the three grinding elements and like the grinding element 9 is of composite character. It consists of an annular series of equidistantly spaced arcuate segments 35 and serves as an instrumentality for medium grinding the glass or other piece being ground after the latter is first rough ground by the arcuate segments 22 that constitute the outer grinding element 9. The arcuate segments 35 are in the form of body parts 36 and abrasive parts 37 and are like the arcuate grinding segments 22 except that they are not as long. The body parts 36 are preferably formed of the same non-abrasive material as the body parts 23 of the segments 22 and similarly fit snugly in, the annular groove 20 between adjacent circular ribs and 16. The outer abrasive parts 37 are soldered or otherwise fixedly secured or bonded to the body parts 36 and consist of matrices and diamond or other abrasive particles that are imbedded in and distributed throughout the matrices. The abrasive particles that constitute a part of the abrasive parts 37 are of medium mesh, as for example, .170 to 200 mesh, in order that in connection with use of the wheel the circular grinding element 10 effects medium grinding of the glass or other piece being ground. The forward grinding surfaces of the abrasive parts 37 are shown as being flat and lying in aplane that extends at right angles to the wheel body 8, although if desired, such surfaces may be convex or rounded. The outer peripheral sides and ends of the outer abrasive parts 37 are shaped or bevelled in the same manner as the peripheral sides and ends of the abrasive parts 24 of the arcuate segments 22. Preferably the inner peripheral sides of the abrasive parts 37 are similarly shaped or bevelled.

As best shown in Figure 4 of the drawings, the arcuate segments 35 constituting the intermediate circular grinding annulus 10 are normally so positioned that the forward grinding surfaces of the abrasive parts 37 are spaced from the front face of the wheel body a distance slightly greater than the corresponding grinding surfaces of the abrasive parts 24 of the arcuate segments 22. In order to compensate or adjust for wear and also to provide for truing each arcuate segment 35 is provided with a screw arrangement whereby it may be adjusted forwardly away from the Wheel body to the desired extent and then releasably locked in place. Such screw arrangement for each of the arcuate segments 35 consists of an outer pair of feed or adjusting screws 38 and an inner pair of locking screws 39. The feed screws 38 and the locking screws 39 are mounted, arranged and constructed like, and function in the same manner as, the feed screws 25 and the locking screws 26 for the arcuate segments 22. Preferably, the arcuate segments 35 are the same in number as the arcuate segments 22 and are so arranged that the spaces between them are circumferentially offset or staggered with respect to the spaces between the ends of the arcuate segments 22. The specific reason for offsetting or staggering will be pointed out hereafter.

The circular grinding annulus 11 is the smallest of the three grinding annulae and like the grinding annulae 9 and 10 is of composite character. It consists of an annular series of equdistantly spaced arcuate segments 40 and serves as an instrumentality for fine grinding the glass or other piece being ground after the latter is first rough ground by the arcuate segments 22 and is then medium ground by the arcuate segments 35. The arcuate segments 40 are in the form of body parts 41 andabrasive parts 42 and are like the arcuate segments 22 and 35 except that they are materially shorter. The body parts 41 are preferably formed of the same non-abrasive material as the body parts of the segments 22 and 35 and fit snugly in the annular groove 21 between the ribs 17 and 18- The abrasive parts 42 of the segments 40 are soldered or otherwise fixedly secured or bonded to the body parts 41 and consist of matrices and diamond or other abrasive particles that are imbedded in the matrices and are distributed throughoutthe latter. The abrasive particles that constitute a part of the abrasive parts 42 are of fine mesh, such for example, as 320 mesh, in order that in connection with use of the wheel the circular grinding element 11 which is composed of the arcuate segments 40 effects fine grinding of the glass being ground. The grinding surfaces of the abrasive parts 42 are shown as being fiat and lying in a plane that extends at right angles to the axis of the disc-like body 8, although if desired such surfaces may be convex or rounded. The outer and inner peripheral sides and the ends of the abrasive parts 42 are shaped or bevelled in the same manner as the abrasive parts of the segments 22 and 35. The aforementioned shaping or bevelling of the inner sides of the abrasive parts 42 of the arcuate segments 40 is of extreme importance because should any portion of the glass or other work piece after being ground by the leading one-half part of the grinding element 11 move in the direction of I the front face of the wheel body due either to resiliency on the part of the support for the glass or other work piece or building up of the hereinafter described coolant between the reverse or opposite side of the glass and the glass support, such portion is engaged by the shaped or bevelled inner peripheral sides of the arcuate segments 40 in the trailing one-half part of the grinding element 11 and hence is not subject to chipping or fracturing. As shown in Figure 4, the arcuate segments 40 are normally so positioned that the outer side surfaces of the abrasive parts 42 are spaced from the front face of the wheel body a distance slightly greater than the outer side surfaces of the abrasive parts 37 of the arcuate segments 35. In order to compensate oradjust for wear and also to permit of truing in conection with wheel assembly, each arcuate segment 40 is provided with a screw arrangement whereby it may be adjusted outwards to the desired extent and then releasably locked in place. Such screw arrangement for each of the arcuate segments 40 consists of an outer pair of feed or adjusting screws 43 and an inner pair of locking screws 44. The feed screws 43 and the locking screws 44 are mounted, arranged and constructed like, and function in the same manner as, the feed screws 25 and the locking screws 26 for the arcuate segments 22. As shown in Figure 1 of the drawings the arcuate segments 40 are the same in number as the arcuate segments 35 and are so arranged or positioned that the spaces between them are circumferentially offset or staggered with respect to the spaces between the ends of said arcuate segments 35. As shown in Fig. 4, the outer peripheral sides of the abrasive parts of the arcuate segments are bevelled to a pronounced degree so that chipping of the glass surface undergoing grinding which ordinarily would take place in the absence of such bevelling will be obviated. It is also to be observed that the forward abrading surfaces of the abrasive parts of each annulus other than the innermost annulus lies in a horizontal plane intermediate the horizontal confines of the next adjacent inner abrasive part.

In order to supply a liquid coolant to the abrasive parts 24 of the arcuate segments 22, the disc-like body 8 of the grinding wheel is provided with a circular groove 45 and an annular series of equidistantly spaced ducts 46. The circular groove 45 is formed in the outer portion of the rear face of the body and is disposed directly above or opposite to the annular space between the outwardly extending circular ribs 14 and 15 on the front face of the wheel body. It is contemplated that the grinding wheel will be driven in one direction only (see arrow in Figure l) and that there will be positioned adjacent to the circular groove 45 a nozzle (not shown) for directing downwards into the groove a stream of any suitable liquid coolant. The ducts 46 extend and establish communication between the annular groove 45 and the an.

asezoes nular space between the ribs 14 and 15. They are straight as shown in Figure 6 and serve to conduct the liquid coolant from the circular groove 45 into the aforementioned annular space between the ribs' 14 and 15. As shown in Figure 1 the ducts correspond in number to the arcuate segments 22 and are so arranged that their lower-or-discha-rge ends are'positioued opposite to the spaces between the ends of said segments. In the direction of their discharge ends, the ducts46 are inclined circumferentially with respect to thewheel body in a direction opposite to the direction of drive or rotation of the wheel body (see Figure 6). They are also inclined outwards as shown in Figures 3 and 4. Because of the manner in which the ducts are inclined, the ducts serve in a fashion as'scoops and direct the liquid coolant downwards towards the leading ends of the arcuate segments 22. The portion of the wheel body 8 that defines the outer side of the circular groove 45 is undercut as at 47 in order-that the liquid coolant that is delivered into the groove is directed toward theupper or receiving ends of the ducts 46. The inner side surface of the rib 14 is flared outwards so that it directs towards the abrasive parts 24 of the arcuate segments 22 the streams of liquid coolant that emanate from the lower or discharge ends of the ducts 46. The excess liquid coolant flows outwards by centrifugal force through the spaces between the arcuate segments 22. By reason of the fact that the inner peripheral portions of said abrasive parts 24 are shaped or bevelled as hereinbefore pointed out, such portions serve effectively to guide or direct the working coolant so'th'at it flows readily between the outer side surfaces of the outer abrasive parts 24 of the segments 22 and the adjacent portion of the glass or other piece being ground.

For the purpose of supplying a coolant in liquid form to the abrasive parts 37 of the arcuate segments 35 the disclike wheel body 3 is provided with a circular groove 48 and an annular series of equidistantly spaced ducts 49. The circular groove 48 is formed in the intermediate portion of the rear face of the bodyan'd is disposed directly above or opposite to the annular space between the outwardly extending circular ribs 16 and 17 on the front face of the wheel body. It is contemplated that there will be positioned adjacent to the circular groove 48 a nozzle (not shown) for directing downwards into the groove a stream of any suitable liquid coolant under pressure. The ducts 49 extend and establish communication between the annular groove 43 and the annular space between the ribs 16 and 17. They are straight and serve to conduct the liquid coolant from the groove 48 into the aforementioned annular space between the ribs 16 and 17. Preferably, the ducts 49 correspond in number to the arcuate segments 35 and are arranged so that their lower or discharge ends are positioned opposite to the spaces between the ends of said segments 35. The angularity or angle of inclination of the ducts 49 is the same as the ducts 46. In other words, the ducts 49 are inclined circumferentially with respect to the wheel body in a direction opposite to the direction of drive or rotation of the wheel body, and are also inclined outwards as shown in Figures 3 and 4. Because of the particular manner in which the ducts are inclined, the ducts serve as scoops and also direct the liquid coolant downwards towards the leading ends of the arcuate segments 35. The portion of the wheel body 8 that defines the outer side surface of the circular groove 43 is undercut as at St? in order that the liquid coolant that is delivered into the groove by the aforementioned nozzle is directed toward the upper or receiving ends of the ducts 49. The inner side surface of the rib 16 is flared outwards so that it directs toward the abrasive parts 37 the streams of liquid coolant that emanate from the discharge ends of the ducts 49. Any excess coolant that is delivered through the ducts 49 and into the annular space between the ribs 16 and 17 flows outwards by centrifugal force through the spaces between the ends of the arcuate segments 35 and then into the annular space between the ribs 14 and 15 where it assists the coolant in the last mentioned space in effecting cooling of the abrasive parts 24 of the arcuate segments 22. By reason of the fact that the inner peripheral sides of said abrasive parts 37 are shaped or bevelled as hereinbefore pointed out, such portions serve effectively to guide or direct the working coolant so that it flows readily between the side surfaces of the outer abrasive parts 37 of the segments 35 and the adjacent portion of the glass or other piece being ground.

In order to supply a coolant in liquid form to the abrasive parts 42 of the arcuate segments 40 that constitute the innermost circular grinding annulus 11, the wheel body 8 is provided withia circular groove 51 and an annular series of equidistantly spaced ducts. 52. The circular groove 5.1 is formed in .the inner portion of the rear face of the body and is disposed a small distance inwards of the outwardly extending circular rib 18. It is contemplated that there will be positioned adjacent to the groove 51 a nozzle (not shown) for directing downwards into the groove a stream of any suitable liquid coolant under pressure. The ducts 52 extend and establish communication between the annular groove 51 and the outer portion of the annular space within the rib 18. They are straight and serve to conduct the liquid coolant into the outer portion of said annular space. Preferably, the ducts 52 correspond in number to the arcuate segments 40 and are so arranged that their lower or discharge ends are positioned directly opposite to the spaces between the ends of said segments 40. As shown in the drawings, the ducts 52 are inclined or angularly disposed in the same manner as the ducts 46 and the ducts 49. In other words, the ducts 52 are inclined circumferentially with respect to the wheel body in a direction opposite to the direction of drive or rotation of the wheel body and are also inclined outwards. Because of the manner in which the ducts 52 are inclined, such ducts serve as scoops and direct the liquid coolant downwards towards the leading ends of the arcuate segments 40. The portion of the wheel body that defines the outer side surface of the groove 51'is undercut as at 53 in order that the liquid coolant that is delivered into the groove 51 is directed toward the upper or receiving ends of the ducts 52. The inner side surface of the outwardly extending rib 18 is flared outwards so that it directs towards the abrasive parts 42 of the arcuate segments 40 the streams of liquid coolant that emanate from the lower or discharge ends of the ducts 52. Any excess liquid coolant that is discharged from the ducts 52 flows outward by centrifugal force through the spaces between the ends of the arcuate segments 40 and mixes with the liquid coolant that is delivered by the ducts 49 into the annular space between the ribs 16 and 17. By reason of the fact that the inner peripheral portions of said abrasive parts 42 are shaped or bevelled as hereinbefore pointed out, such portions serve effectively to guide or direct the working coolant so that it flows readily between the outer side surfaces of the outer abrasive parts 42 of the segments 40 and the adjacent portion of the glass or other piece being ground.

It is contemplated that the liquid coolant which is used in connection with use of thegrinding wheel will have a low surface tension in order that it serves not only to effect the desired cooling but also effectively to clean or remove the ground particles or sludge from the abrasive parts of the arcuate segments 22, 35 and 40. The purpose in having the spaces between the segments 35 circumferentially offset or staggered with respect to the spaces between the segments 22 and the spaces between the segments 4%! is to cause the liquid coolant to be subjected to a bathing or sinuous flow action as it flows successively radially outwards through the spaces between the three circular grinding elements. By subjecting the coolant to the aforementioned baffling or sinuous flow action, it effects maximum cooling and also maximum cleaning or re moval of the ground particles from the abrasive parts of the various arcuate segments.

In connection with'use of the grinding wheel thepiece 7 to be ground will first be positioned adjacent to but radially outwards from the front face of the wheel. In addition, it will be positioned in parallel relation with the front face of the wheel body and so that the inner side surface thereof is positioned a small distance nearer to said front face of the wheel body than the outerside surfaces of the abrasive parts 24 of the'farcuate segments 22 that constitute the outermost circular grinding annulus 9.

After the glass piece 7 is positioned and arranged in the aforementioned manner the wheel is caused to be driven at a comparatively high speed by its power driven shaft, liquid coolant is delivered into the circular grooves 45, 48 and 51 by the aforementioned nozzles, and the piece and wheel are moved relatively to one another in a plane at right angles to the axis of the wheel. In connection with relative movement of the glass piece and the wheel, the outermost grinding annulus 9 first rough grinds the adjacent surface of the glass piece to a certain depth, then the intermediate circular grinding annulus 10 medium grinds said adjacent surface of the glass piece to a slightly greater depth, and finally the innermost circular grinding annulus 11 fine or finish grinds said adjacent surface of the glass piece to a slightly greater depth, as indicated or illustrated in Figure 4.

The herein described composite grinding wheel due to its particular construction and design possesses extremely high efliciency and may be operated at a comparatively low cost. In addition, it grinds in a multiple fashion and at a high rate of speed and may be producedat a comparatively low cost. In effect the wheel serves as or constitutes a plurality of concentrically arranged circular grinding elements on a power driven shaft.

Whereas the grinding wheel has been described as being primarily designed for use in the grinding of glass, it is to be understood that it may be used equally as well in grinding marble, stone, ceramic and other similar materials. It is also to be understood that the abrasive particles of the abrasive parts of all arcuate segments may be the same or practically the same in mesh and that the invention is not to be restricted to the details set forth since they may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

The present application is a continuation-in-part of application Serial 562,965, filed by me on February 2, 1956.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

l. A rotary multiple grinding wheel for grinding a flat surface on a piece of glass or similar material, said grinding wheel comprising a rigid disc-like body adapted to have the central portion thereof connected drivably to one end of a power driven shaft the axis of which is at right angles to said flat surface, and a plurality of circular, spaced apart, concentrically arranged grinding annulae mounted fixedly on the front face of the body and having forward parts in the form of matrices with abrasive particles therein, said parts presenting forward grinding surfaces, said annulae being so disposed that the grinding surfaces of their respective parts are stepped With respect to the front face of the wheel body with the grinding surface of the forward part of the inside annulus of smallest radial extent being spaced forwardly from said front face of the wheel body a distance greater than the grinding surface of the forward part of the outside annulus of largest radial extent, and the grinding surface of the forward part of each annulus other than the inside annulus of smallest radial extent lies in an imaginary plane which is perpendicular to the axis of rotation of the wheel body and intersects the forward part of the next adjacent annulus on the inside of each such annulus.

2. A multiple grinding wheel according to claim 1 and wherein the forward part of the innermost annulus of smallest radial extent has its inside and outside circular edge'regions bevelled so as to slope rearv'vardly in diverg ing relationship. 1

3. A multiple grinding wheel according to claim 1 and in which each grinding annulus is comprised of a rear metallic non-abrasive supporting ring to which the forward abrasive part of the annulus is secured 4. A multiple grinding wheel according to claim 1 and in which each of the circular grinding annulae is of composite character, consists of an annular series of spaced apart arcuate segments, andhas the forward abrasive parts of its segmentsshaped so that they are of progressively decreasing width in a forward direction to a pronounced degree.

5. A multiple grinding wheel according to claim 1 and in which each of the circular grinding annulae is of composite character, consists of an annular series of spaced apart arcuate segments, and has the ends of the outer abrasive parts of its segments shaped so that they are of progressively decreasing width in a forward direction to a pronounced degree, and the inner peripheral portions of the outer abrasive parts of the acuate segments of the innermost circular grinding annulus are shaped similarly to said ends.

6. A multiple grinding wheel according to claim 1 and in which the circular grinding annulae are of composite character and consist of annular series of equidistantly spaced arcuate segments, each of the annulae has the same number of arcuate segments as the other annulae and is so arranged that the spaces between the ends of its segments are circumferentially offset or staggered with respect to the spaces between the ends of the segments of the adjacent annulae, and the body has means for flowing liquid coolant through it and towards the segments.

7. A multiple grinding wheel according to claim 1 and wherein the fixed mounting for said grinding annulae on said wheel body comprises a plurality of widely radially spaced concentric annular grooves one for each annulus, formed in the front face of said wheel body and into which grooves the rearmost portions of the annulae fit snugly in radially interlocking relationship.

8. A multiple grinding wheel according to claim 1 and in which each of the circular grinding annulae is of composite character and consists of an annular series of spaced apart arcuate segments, and each of the arcuate segments has associated with it an individual screw arrangement whereby it may be adjusted to or from the body and then releasably locked in place.

9. As a new article of manufacture, a grinding wheel comprising a circular rigid disc-like body adapted to have the central portion thereof connected drivably to one end of a power driven shaft and provided in the front face thereof with a concentrically arranged comparatively shallow groove, an annular series of spaced apart arcuate segments positioned adjacent to the front face of, and ar ranged in concentric relation with, the body, having the inner and outer peripheral sides fitting slidably in, and in radial interlocked relation with, the groove, and having the forward portions thereof in the form of matrices with abrasive particles therein, and a plurality of screw arrangements corresponding in number to, and associated respectively with, the segments, extending between the body and the segments, and operative to effect individual adjustment of the segments towards and away from the body and then releasably lock them in place.

10. A grinding Wheel according to claim 9 and in which each screw arrangement consists of two feed screws which extend through, and are in interfitting relation with, transverse screw threaded open ended holes in the wheel body, have the ends thereof that are adjacent to the front face of the body in abutment with the ends of the associated arcuate segment, and embody at their other ends means whereby they may be turned, and at least one locking screw which is disposed between the two feed screws, extends loosely through a cylindrical open ended transverse hole in the body, has the end thereof that 11 is adjacent to the front face of the body mounted in, and in'interfitting relation with, a screw threaded socket in said associated segment, and embodies at its otherend an enlarged head that'fits within a counterbore at'the adjacent end of the cylindrical hole and embodies means whereby it may be turned.

References Cited in the file of this patent UNITED STATES PATENTS 12 Beth Feb. 17, 1925 Hitchock Oct. 4, 1927 Holt, July 21, 1931 Jopp Oct. 20, 1931 Fraser Jan. 19, 1932 Hanus Mar. 20, 1934 Penny Aug. 18,1936 Raber Dec. 7, 1937 Simmonds May 21, 1940 Strnad Mar. 20, 1956 FOREIGN PATENTS 7 Germany Nov. 10, 1907 

